Messages in this thread |  | | | Subject | Re: [PATCH 6/3] perfcounter: Substract the buffer size field from the event record size | | From | Peter Zijlstra <> | | Date | Mon, 10 Aug 2009 16:13:05 +0200 |
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On Mon, 2009-08-10 at 16:11 +0200, Frederic Weisbecker wrote:
> From: Frederic Weisbecker <fweisbec@gmail.com> > Date: Mon, 10 Aug 2009 15:56:46 +0200 > Subject: [PATCH 6/3] perfcounter: Substract the buffer size field from the event record size > > We compute the perf raw sample size by aligning the raw ftrace event > size plus the buffer size field itself. We do that instead of aligning > only the perf raw sample size, so that we might economize some in some > cases. > > But this buffer size field is not stored in the perf raw sample, we > must then substract its size from the buffer once we computed the > alignment unless we may get a useless u32 field in the buffer. > > Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Thanks!
> --- > include/trace/ftrace.h | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletions(-) > > diff --git a/include/trace/ftrace.h b/include/trace/ftrace.h > index 4dc1a60..f98ff56 100644 > --- a/include/trace/ftrace.h > +++ b/include/trace/ftrace.h > @@ -639,7 +639,12 @@ __attribute__((section("_ftrace_events"))) event_##call = { \ > * pc = preempt_count(); > * > * __data_size = ftrace_get_offsets_<call>(&__data_offsets, args); > - * __entry_size = __data_size + sizeof(*entry); > + * > + * // Below we want to get the aligned size by taking into account > + * // the u32 field that will later store the buffer size > + * __entry_size = ALIGN(__data_size + sizeof(*entry) + sizeof(u32), > + * sizeof(u64)); > + * __entry_size -= sizeof(u32); > * > * do { > * char raw_data[__entry_size]; <- allocate our sample in the stack > @@ -689,6 +694,7 @@ static void ftrace_profile_##call(proto) \ > __data_size = ftrace_get_offsets_##call(&__data_offsets, args); \ > __entry_size = ALIGN(__data_size + sizeof(*entry) + sizeof(u32),\ > sizeof(u64)); \ > + __entry_size -= sizeof(u32); \ > \ > do { \ > char raw_data[__entry_size]; \
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